Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$143.85	5.746%	$152.1156	$152.12	$152.10	$152.10
Purchase #2	$90.49	9.424%	$99.0178	$99.02	$99.00	$99.00
Purchase #3	$94.47	12.402%	$106.1862	$106.19	$106.20	$106.20
Purchase #4	$40.96	10.697%	$45.3415	$45.34	$45.35	$45.30
Purchase #5	$65.92	13.569%	$74.8647	$74.86	$74.85	$74.90
Purchase #6	$14.65	8.345%	$15.8725	$15.87	$15.85	$15.90
Purchase #7	$37.27	6.219%	$39.5878	$39.59	$39.60	$39.60
7 purchase totals =	$487.61		$532.9861	$532.99	$532.95	$533.00